One of the best newssites for wow - but unfortunatly all in german:
http://wow.ingame.de/content.php?c=71949
The link leads to a very good The Eye Guide.
Interesting what that guy wrote about the hardness of the bosses - 10 is hardest and 1 is very easy.
Al'ar: Leicht über Magtheridon Schwierigkeitsgrad: 4 (a bit over Mag hardness)
Leerhäscher: Gleichzusetzen mit Gruul Schwierigkeitsgrad: 2 (same as Gruul)
Solarian: Seit 2.2 leichter als A'lar aber noch Schwieriger als Leerhäscher
Schwierigkeitsgrad: 3 (since 2.2 easier as Alar but harder then VR)
Prinz Kael'thas: Einer der schwersten Burning Crusade Bosse. Schwierigkeitsgrad: 9 (one of the hardest BC Bosses)
Hier a excellent guide for A`lar. Also with a Video which is commented to download. 414 mb, but ofc also in german:
http://wow.ingame.de/content.php?c=72013
Everybody that understands german should really check it out !